The present invention is related to a bump structure of a scattering reflective board and a method for manufacturing the bump structure. The pattern of the optical mask is composed of multiple regularly arranged strips and multiple irregularly arranged circles. After exposed and developed, multiple scattering bumps are formed on the reflective board.
A conventional semi-reflective or reflective liquid display employs an internal reflective board to which a scattering film is externally attached. The environmental light will pass through the scattering film twice so that the reflectivity is lowered and the problem of aberration tends to take place.
In the case that the scattering film is made inside the liquid crystal display, that is, under the reflective layer, the problem of aberration can be avoided. After yellow light manufacturing procedure, the substrate is heated and inclined to make the bumps create reflow effect. Then the resin is twice painted. By means of many times of exposure and gray stair optical mask, asymmetric bump structures are achieved.
FIG. 4 shows a conventional method for manufacturing reflective board with bumps by way of reflow effect. A photoresistor layer 62 is painted on the substrate 61 and an optical mask is used for exposure and development to form multiple protuberances 621. Then the substrate 61 is inclined and heated. Thereafter, the protuberances 621 on the surface of the substrate 61 will be softened. Due to gravity, the softened photoresistor will flow downward to achieve a reflow effect and form asymmetrical arch shape. Finally, a metallic layer is fully deposited on the surfaces of the substrate 61 and the deformed protuberances 621 to form a reflective layer 64 with multiple asymmetrical protuberances 621. The reflective layer 64 serves to scatter and reflect the light by predetermined angle.
In the above manufacturing procedure of the reflective board, the photoresistor is etched by etching liquid. Actually, the etching depth is very small. Accordingly, in heat treatment, due to the reflow effect, the deformation amount of the downward flowing protuberances 621 will be very unapparent or even it is very hard to control the deformation amount within a predetermined range. As a result, the shape of the deformed protuberances 621 is hard to control.
FIG. 5 shows another conventional measure for manufacturing reflective board with bumps by means of parallelly moving the opticall mask and repeated exposure. A photoresistor 72 is painted on a substrate 71. Then, in yellow light manufacturing procedure, the optical mask 73 is parallelly moved to repeatedly expose the photoresistor 72. By means of many times of exposure, due to different exposure amounts, after developed, the photoresistor 72 is formed with stair-like protuberances 721. The substrate 71 with the stair-like protuberances 721 is heated to melt and dull the stair-like protuberances 721 so as to form an asymmetrical pattern. The surfaces of the asymmetrical protuberances 721 form bump structures of a scattering reflective board.
In the above measure, the stair-like protuberances 721 are formed by many times of exposure. The displacement of the optical mask between exposures is very small and hard to accurately control. Also, it is hard to accurately form the stair-like protuberances.
FIG. 6 shows still another conventional measure for manufacturing reflective board with bumps by means of gray stair optical mask exposure. According to this measure, it is necessary to first manufacture a gray stair optical mask 81 having multiple opaque portions 811, slightly transparent portions 812, semi-transparent portions 813 and fully transparent portions 814. After the photoresistor 83 painted on the substrate 82 is exposed, the different regions create different exposure amounts. Through the development, the region with more exposure amount has deeper development depth so as to form stair-like protuberances 831. Then the protuberances are heated and dulled to form the necessary bumps.
The gray stair optical mask is formed with regions with different exposure amounts. Actually, the bumps of the reflective board are very small and it is necessary to form the gray stair within a very small region. Therefore, it is very hard to manufacture the optical mask and the manufacturing cost is very high.
By means of all the above conventional measures, reflective boards with different patterns of scattering bumps can be manufactured. However, many problems exist in the conventional measures.
Besides, another problem exists in the conventional reflective board with scattering bumps. That is, the scattering bumps solve the aberration problem by means of enhancing the scattering (fogging) of the light. However, the enhanced scattering of the light will make it hard to concentrate the light. This will lead to insufficient brightness within visible angle range.
Therefore, it is necessary to provide an improved reflective board with scattering bump structures.